This proposal is for the first phase of a two-phase project to develop a comprehensive model of the age-related barriers and difficulties that discourage driving, or reduce safety, for older motorists. This uniquely comprehensive program incorporates perceptual, cognitive, and motor capabilities, social and environmental factors, travel characteristics and preferences, health status, situational factors, etc. The model will provide a reasonably complete picture of the factors that limit the willingness or ability of older motorists to drive, will indicate the possible interaction of key factors, and where possible will provide quantitative or order-of-magnitude indications of the magnitude of the effects. The approach is based upon the integration of existing models, or known quantitative relationships, identified in diverse technical literatures (including transportation, health, gerontology, behavioral sciences, etc.). The Phase I proposal addresses the identification and initial evaluation of existing models and data. Phase II will include detailed evaluation, model integration and development, and software development for producing the comprehensive model. The model will serve as a basis for programs and efforts in transportation planning, support services, highway safety, policy, and education/training or other direct programs for the elderly.